Consequences of the close relation between Rortex and swirling strength

Direct consequences stem from the close relation between the recently proposed vortex vector (Rortex) and the swirling strength. It is shown that these vortex-identification methods share some relevant properties: (i) both provide the same and, practically, the largest vortex region, (ii) both allow an unlimited uniaxial stretching described by an axisymmetric strain rate, so the strain-rate magnitude inside a vortex may become much larger (without any limitation) than the vorticity magnitude, and (iii) both exhibit a discontinuous outcome, known as the so-called disappearing vortex problem.